Congenital hearing loss in Malta : a survey

The congenitally deaf infant who acquires deafness prior to development of language present special problems when compared to other hearing impaired individuals. This is because both the development of speech and of language depends on adequate hearing. As speech and language are our prime means of communication, the congenitally deaf child is automatically also handicapped in his psychological development, social adaptation and work adaptability. The authors reviewed cases of congenital hearing loss presenting on a 20 year period to establish the incidence of congenital hearing impairment in the Maltese islands; to determine the common causes; to highlight any difficulties in early diagnosis and management of these children.peer-reviewe

Conjuntos excepcionais e alguns problemas de Mahler

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Matemática, 2017.Seja f uma função inteira e transcendente. Denotamos por Sf o conjunto de todos os α ∈ ´Q tais que f(α) ∈ ´Q (o conjunto excepcional de f). Nessa dissertação, mostraremos quais subconjuntos de ´Q podem ser o conjunto excepcional de alguma função inteira e transcendente. Além disso, trataremos de dois problemas de Mahler relacionados a propriedades de funções inteiras e transcendentes. Mostraremos que existem funções inteiras e transcendentes que levam um subconjunto dos números de Liouville nele mesmo e daremos uma resposta positiva ao Problema B de Mahler: Problema B: Existe uma função inteira e transcendente f(z) = Σn =0 ∞ a nz n com coeficientes racionais tal que f( ´Q ) ⊆ ´Q e f−1( ´Q ) ⊆ ´Q ? .Let f be an entire transcendental function. We denote by Sf the set of all α ∈ ´Q such that f(α) ∈ ´Q (exceptional set of f). Throughout this dissertation, we will show which subsets of ´Q can be the exceptional set of some entire transcendental function. Moreover, we will deal with two of Mahler’s problems related to properties of entire transcendental functions. We will show that there are entire transcendental functions that map a subset of Liouville numbers in itself and we will give a positive answer for Mahler’s Problem B: Problem B: Is there an entire transcendental function f(z) = Σn =0 ∞ a nz n with rational coefficients such that que f( ´Q ) ⊆ ´Q e f−1( ´Q ) ⊆ ´Q ?

Stretched-exponential relaxation of birefringence in a critical binary mixture

Transient electric birefringence in near-critical binary mixtures is found to exhibit stretchedexponential relaxation of the form exp[-( t /~) ' ] , with x constant and r diverging as a power law in reduced temperature. A simple scaling theory of this phenomenon is proposed, relating x and the relaxation-time exponent to static and dynamic critical exponents, with values in good agreement with experiment. The results yield information about the distribution of fluctuations in the one-phase region of critical fluids and mixtures. When the elementary relaxation processes in a system are characterized by a broad distribution of relaxation times, its time evolution following a perturbation may be highly nonexponential. In systems as diverse as amorphous solids, materials with random "traps," polymers, and spin glasses, the time dependence of the relaxation function R ( t ) of some dynamical variable may take on the so-called stretched-exponential f0rm~9~ where the exponent x 5 1, and T may be interpreted as a mean relaxation time. In contrast, when the distribution of relaxation rates is very narrow, one finds x = 1. In understanding the nonexponential relaxation found in a given experiment, it is often postulated4 that R ( t ) may be written as a sum, over the distribution of processes P(l), of the exponential behavior each would have in isolation, characterized by a time constant q; where S(l) is a signal function describing the contribution of each process to the observed signal. The index 1 may represent, for instance, the heights of barriers hindering rotation of molecules within a host crystal. The stretched form (1) can be derived from a saddle-point analysis of (21, in the limit of long times, with the exponent x and time constant T related to the relaxation mechanisms and the form of the distribution. while a description such as (2) is a useful representation of the data, there are few systems in which there exist microscopic theories of both the distribution P(l) and of the relaxation time T/ so that the origin of the particular exponent x in (1) is not clear. We report6 here experimental studies of the time dependence of electric birefringence7 near the consolute point of the binary mixture 2,6-lutidine and water which demonstrate stretched-exponential growth and decay of polarization consistent with Eq. (11, with ~~0 . 4 independent of temperature and T= d s ) diverging with reduced y ^ 1 .a. A simple scaling theory is developed which relates the exponents x and y to static and dynamic critical exponents where ~~0 . 0 4 describes the decay of correlations at Tc, z Z 3 is the dynamic exponent for a conserved order parameter,* and ~~0 . 6 3 is that of correlation length £ The present work was motivated by the discovery of analogous stretched-exponential relaxation in micellar solutions of nonionic surfactants near their lower consolute poink9 In order to ascertain whether the anomalous relaxation was a property attributable to the specific microstructure of the systems, with their polydisperse distribution of large micellar aggregates, or, rather, was intrinsic to the critical-point region, we undertook the present experiments on the well-studied lutidine-water solutions. lo Similar results, particularly with regard to the stretched exponential form of the transients, have been found in the butoxiethanol-plus-water system. l

Lipid-based nanoparticles for contrast-enhanced MRI and molecular imaging

In the field of MR imaging and especially in the emerging field of cellular and molecular MR imaging, flexible strategies to synthesize contrast agents that can be manipulated in terms of size and composition and that can be easily conjugated with targeting ligands are required. Furthermore, the relaxivity of the contrast agents, especially for molecular imaging applications, should be very high to deal with the low sensitivity of MRI. Lipid-based nanoparticles, such as liposomes or micelles, have been used extensively in recent decades as drug carrier vehicles. A relatively new and promising application of lipidic nanoparticles is their use as multimodal MR contrast agents. Lipids are amphiphilic molecules with both a hydrophobic and a hydrophilic part, which spontaneously assemble into aggregates in an aqueous environment. In these aggregates, the amphiphiles are arranged such that the hydrophobic parts cluster together and the hydrophilic parts face the water. In the low concentration regime, a wide variety of structures can be formed, ranging from spherical micelles to disks or liposomes. Furthermore, a monolayer of lipids can serve as a shell to enclose a hydrophobic core. Hydrophobic iron oxide particles, quantum dots or perfluorocarbon emulsions can be solubilized using this approach. MR-detectable and fluorescent amphiphilic molecules can easily be incorporated in lipidic nanoparticles. Furthermore, targeting ligands can be conjugated to lipidic particles by incorporating lipids with a functional moiety to allow a specific interaction with molecular markers and to achieve accumulation of the particles at disease sites. In this review, an overview of different lipidic nanoparticles for use in MRI is given, with the main emphasis on Gd-based contrast agents. The mechanisms of particle formation, conjugation strategies and applications in the field of contrast-enhanced, cellular and molecular MRI are discussed